The purpose of this research project is to determine the fate of amines including norepinephrine (NE) and 5-hydroxytryptamine (5-HT) by newborn rabbit lungs. The alteration of uptake under control conditions in the newborn rabbit will be compared with the rates in the presence of inhibitory drugs such as cocaine. Determinations will be made at various ages and at various pulmonary artery pressures. The method used will be that of Gillis and Iwasawa whereby isolated right and left lungs are perfused simultaneously and independently with Krebs medium with collection of the effluent of each lung at timed intervals. NE and 5-HT will be measured fluorometrically on an American Instrument Co. spectrofluorometer (SPF-125). When radioactive substances are perfused, a Packard 3320 liquid scintillation spectrometer will be used to measure radioactivity. Identifying the extent to which the newborn lung functions as a metabolic organ will permit 1) an appreciation of the consequences of "short circuiting" the lung in the newborn, i.e., cardiopulmonary bypass; 2) assessment of the effects of certain pharmacologic agents in the newborn as compared to the adult; 3) definition of the role of amines in the possible production of pulmonary disease, i.e., hyaline membrane; and 4) our further understanding of catecholamine support of the circulation of the neonate.